One known technique for a storage system achieves higher performance and availability of the storage system with a plurality of storage devices forming a cluster, and a host computer evenly issuing an I/O request to the storage devices in the cluster (PTL 1). Another known technique for a storage system achieves higher performance and availability of the storage system with a plurality of processor modules (hereinafter, referred to as “processors”) controlling a single channel, and one of the processors that has received the I/O request from the host computer assigning the I/O request to another one of the processors (PTL 2).